There are in the prior art many variations of two axis flexures. One variation is disclosed in U.S. Pat. No. 3,354,726, entitled "Two-Axis Gyro" and issued to W. J. Krupick and R. F. Cimera and assigned to the same assignee as the present invention.
The above patent describes a free-rotor type gyroscope having a flexure hinge for interconnecting the gyro rotor to a driven motor shaft. The flexure suspension comprises an inner hinge unit fixedly connected to an outer hinge unit in a generally concentric and parallel manner. Each hinge unit is composed of three gimbals; namely, an upper, middle, and lower and has two quadrature pairs of oppositely disposed flexure bars for interconnecting the gimbals and for permitting relative tilting of the gimbals about any transverse axis perpendicular to the hinge's central axis. The upper gimbals of the respective hinge units are fixedly coupled together and to the gyro's rotor, whereas the lower gimbals of the two hinge units are fixedly connected to each other and to the gyro's spin shaft, respectively. The inner hinge provides high stiffness axially, i.e., along the gyro's spin axis. The outer hinge is designed to provide radial stiffness along the plane perpendicular to the spin axis. In the above device, each flexure assembly had four flexures made by grinding two adjacent holes and/or gimbals made selective by selective milled cuts.